A three-year study of the nation's drinking water quality has found more than 200 unregulated chemicals in the tap water of 45 states.

The Environmental Working Group analysis of 20 million tap water quality tests found a total of 316 contaminants -- including industrial solvents, weed killers, refrigerants and the rocket fuel component perchlorate -- in water supplied to the public between 2004 and 2009.

U.S. EPA regulates 114 of those pollutants, setting maximum legal levels that water utilities achieved 92 percent of the time, according to the study.

EWG frets that the remaining chemicals, which have no mandatory federal safety standards, can come in potentially toxic combinations for long-term consumption.

"Utilities do the best job that they can treating a big problem with limited resources, but we must do better," said Jane Houlihan, the group's senior vice president for research. "It is not uncommon for people to drink tap water laced with 20 or 30 chemical contaminants. This water may be legal, but it raises serious health concerns."

The pollutants derive from a wealth of sources, including agriculture, factory discharges, consumer products, urban runoff and wastewater treatment plants.

The annual water quality reports that utilities are required to send customers provide a partial picture, the study says, as they contain no information on unregulated chemicals. They also provide average levels of most contaminants, which do not reveal if there were short periods when chemicals spiked past legal limits.

EPA in September said it was considering regulating 104 additional chemicals in tap water, including pesticides, commercial chemicals, disinfection byproducts, and for the first time, pharmaceuticals.

The list was the longest ever compiled by the agency under a 1996 law requiring it to evaluate possible tap-water pollutants every five years and make regulatory determinations for at least five of them.

EPA said it will continue to research the contaminants and will determine by 2013 whether to propose drinking water regulations for some of them.

The EWG study says the nation should adopt new policies for drinking water that include regulating more contaminants and spending more money on measures that prevent pollution.

While water utilities across the country spend more than $50 billion a year to treat drinking water, the nation spends $207 million a year to protect source waters and prevent pollution from sources such as urban runoff, the study says.

The report recommends investing more money in conserving land in buffer zones around public water supplies.

It also suggests that EPA "greatly expand" requirements for testing water for unregulated contaminants and that Congress provide more money to get the testing done.

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